"In the last few years, there has been a large increase in awareness of treating pain in horses; many practitioners want to know how to do it better," began Nora Matthews, DVM, Dipl. ACVA, professor of anesthesia at Texas A&M University. During the 2009 American Association of Equine Practitioners Convention, held Dec. 5-9 in Las Vegas, Nev., she discussed the current usage of analgesics (painkillers) in equine medicine and what's needed to improve their use.

The advantages of using painkillers in horses are that they help an injured or ill horse feel better, eat more, lose less weight, stay in the hospital for a shorter time, and often avoid chronic pain, she explained. The potential disadvantages include the possibility that the horse makes the injury worse by being too active because he doesn't hurt as much, the fact that painkillers can slow down the GI tract (potentially contributing to colic), the high cost of many painkillers, and the fact that masking pain can also mask any worsening of the painful condition.

Since a horse can't tell you when, where, or how badly he hurts, veterinarians have to assess his pain by evaluating physical mechanisms (such as heart rate and levels of cortisol, often called the stress hormone), responses to pressure on the sore area, changes in force plate results for lameness cases, and changes in behavior. One of the hardest things about studying pain in horses is that there are various systems for grading pain and improvement; it's much more difficult to objectively assess pain than "harder" targets such as levels of substances in the bloodstream.

Painkillers can be given in a variety of ways, whether systemically (orally, intravenously, intramuscularly, etc.) or locally to block pain in a specific area of the body. Matthews expressed hope for the newer transdermal (through the skin) analgesic options, which are less invasive than many other administration routes and thus better tolerated by horses and their owners.

Non-steroidal anti-inflammatory drugs (NSAIDs) such as Bute (phenylbutazone) and Banamine (flunixin meglumine) are the "mainstays" of equine analgesia as they reduce the pain of inflammation, reported Matthews. However, there are many other classes of analgesics used in horses and many ways to give them; she described the advantages, disadvantages, and modes of action of all of them.

"Balanced analgesia is important, in which we use several different drugs that work on different receptors," she noted. "Lower doses of each drug equal fewer side effects."

She advised treating pain early when possible, rather than waiting until a horse is three-legged lame or refusing to eat. "If we wait until pain is agonizing, then we often can't control it," she explained. "This should be expected from what is known about pain. Our expectations for analgesics must be realistic, and we should measure food and water consumption (to note any changes that might be due to significant pain)."

Matthews finished her talk with the following wish list for equine painkillers:

  • Universal pain scoring system for horses so all veterinarians and researchers are on the same page when evaluating and comparing analgesic effects.
  • Practical delivery methods for analgesics.
  • More formulations of currently used drugs so they can be given via different routes depending on the patient's problem and situation.
  • More information about analgesics and their effects on gastrointestinal motility, including more information on common drug combinations.
  • New drugs/formulations that will be long-acting, can be given orally, and are practical for field use.

"Effective treatment of equine pain is what every equine practitioner strives to achieve," she stated. "However, the profession is still a long way from the ultimate goal, and much research and information are still needed."

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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